Rotary impact motor

ABSTRACT

IN A ROTARY BIDIRECTINALLY OPERABLE IMPACT MOTOR FOR POWER DRIVEN FASTENER SETTING TOOLS A RECESSED IMPACT DOG IS JOURNALLED BY ITS CYLINDRICAL BACK PORTION EXTENDING OVER MORE THAN 180 DEGREES IN A JOURNALLING RECESS OF A HAMMER BODY PIVOTALLY ABOUT AN AXIS SPACED FROM BUT PARALLEL WITH THE AXIS OF ROTATION OF THE HAMMER BODY FOR TAKING IMPACT AND RELEASE POSITIONS WITH RESPECT TO OPPOSED IMPACT SURFACES ON AN ANVIL COAXIAL WITH THE HAMMER BODY AND SURROUNDED BY A ROTATION CAVITY THEREIN. THE JOURNALLING RECESS IS OF LARGER DIAMETER THAN SAID ROTATION CAVITY. END SURFACES ON THE IMPACT DOG COOPERATE WITH THE ANVIL FOR PIVOTING THE IMPACT DOG TO IMPACT POSITION WHILE A DRIVE ELEMENT FOR THE HAMMER BODY ENGAGES THE IMPACT DOG FOR PIVOTING IT TO THE RELEASE POSITION. THE END SURFACES ARE TRANSVERSE TO THE BACK PORTION OF THE IMPACT DOG AS WELL AS THE RECESS THEREOF.

P 21, 1971 K. c. SCHOEPS 3,606,932

, ROTARY IMPACT MOTOR Filed June 16, 1970 ZSheets-Sheet 1 Se t. 21, 1971K. c. SCHOEPS 3,606,932

ROTARY IMPACT MOTOR Filed Jun 16, 1970 2 Sheets-Sheet United StatesPatent 3,606,932 ROTARY IMPACT MOTOR Knut Christian Schoeps, Nacka,Sweden, assignor to Atlas Copco Aktiebolag, Nacka, Sweden Filed June 16,1970, Ser. No. 46,765

Claims priority, application Sweden, June 19, 1969,

Int. Cl. B25d 15/00 US. Cl. 17393.5 7 Claims ABSTRACT OF THE DISCLOSUREIn a rotary bidirectionally operable impact motor for power drivenfastener setting tools a recessed impact dog is journalled by itscylindrical back portion extending over more than 180 degrees in ajournalling recess of a hammer body pivotally about an axis spaced frombut parallel with the axis of rotation of the hammer body for takingimpact and release positions with respect to opposed impact surfaces onan anvil coaxial with the hammer body and surrounded by a rotationcavity therein. The journalling recess is of larger diameter than saidrotation cavity. End surfaces on the impact dog cooperate with the anvilfor pivoting the impact dog to impact position while a drive element forthe hammer body engages the impact dog for pivoting it to the releaseposition. The end surfaces are transverse to the back portion of theimpact dog as well as the recess thereof.

The invention relates to a rotary impact motor of the kind used inconnection with fastener setting tools, impact wrenches and the like. Insuch applications is formerly known a type or rotary impact motor withimpact action in both rotational directions thereof against therespective of a pair of opposed impact surfaces on a rotatable anvil, inwhich impact motor a hammer body is carried rotatably coaxially withrespect to the axis of rotation of the anvil. The hammer body surroundsthe anvil and the impact surfaces thereof by a rotation cavity. A partlycylindrical journalling recess in the hammer body opens out into therotation cavity. An impact dog has a recess thereon facing the anvil anda partly cylindrical back portion which is supported in the journallingrecess for pivotal movement of the impact dog about an axis spaced frombut parallel with the axis of rotation of the anvil for takingrespectively impact or release position relative to one of the impactsurfaces of the anvil. One of the opposed end portions of the impact dogcooperates with the anvil for pivoting the impact dog to impact positionand a rotatable drive means is in operative engagement with the impactfor pivoting it to release position. The opposed end portions of theseformerly known impact motors have always been designed sharply pointedproviding cam edges for cooperation with the anvil and impact deliveringsurfaces in immediate adjacency to the edges.

In the impact motors of the above type there occurs at certaintolerances a canting of the impact dog in the journalling recess byreason of the impact dog tending to fall out into the rotation cavity ofthe hammer body. The sharply pointed edge and impacting portions of theimpact dog and the impact surfaces of the anvil may in such case,because of the unfavourable force distribution, be rapidly fragmented topieces. For purposes of counteracting this occurrence there has inconnection with the journalling previously been provided a specialforward supporting groove in the interior of the hammer for positivelyjournalling the forward end of the impact the production cost.

3,606,932 Patented Sept. 21, 1971 ice It is therefore an object of theinvention to provide a rotary impact motor of the above stated type inwhich the journalling of the impact dog is less sensitive to tolerancesand assures a better guidance for the impact dog than before.Simultaneously the journalling of the impact dog is to be simplified andthe impact surfaces, the impact dog, and the anvil have to be so adaptedto one another in their cooperation that the non-sensitiveness totolerances is supported by an improved shape of the cooperating parts inrespect of attaining better strength.

For the above and other purposes there is according to the inventionprovided a rotary impact motor with impact action in both rotationaldirections thereof comprising a housing, a rotatable anvil in saidhousing, opposed impact surfaces on said anvil, a hammer body rotatablycarried in said housing coaxially with respect to the axis of rotationof said anvil, a rotation cavity in said hammer body surrounding saidanvil and said impact surfaces thereof, a partly cylindrical journallingrecess in said hammer body opening up into said rotation cavity thereofand of larger diameter than said rotation cavity an impact dog having arecess thereon facing said anvil and a partly cylindrical back portionextending over more than degrees and supported in said journallingrecess for pivotal movement about an axis spaced from but parallel withsaid axis of rotation for taking respectively impact or release positionrelative to one of said impact surfaces, opposed end surfaces on saidimpact dog transverse to said back portion and intersecting said recessthereof, one of said surfaces cooperating with said anvil for pivotingsaid impact dog to said impact position, and rotatable drive means insaid housing in operative engagement with said impact dog for pivotingsaid impact dog to said release position.

The above and other purposes of the invention will become obvious fromthe following description and from the following description and fromthe accompanying drawings in which three embodiments of the inventionare illustrated by way of example. It should be understood that theseembodiments are only illustrative of the invention and that variousmodifications thereof may be made within the scope of the appendedclaims.

In the drawings FIG. 1 shows a longitudinal section through an impacttool comprising a rotary impact motor according to the invention. FIG. 2is a cross section on the line 2--2 in FIG. 1. FIGS. 3 and 4 are crosssections respectively on the lines 3-3 and 44 in FIG. 1 when the rotaryimpact motor is in impact position. FIGS. 5 and 6 correspond to theFIGS. 3 and 4 but show the rotary impact motor in release positionimmediately after impact. FIGS. 7-9 show the parts of the impact motorin three different intermediate positions between the release positionin FIG. 6 and the impact position in FIG. 4 of the impact dog. FIG. 10and FIG. 11 show cross sections corresponding to FIG. 4 and FIG. 6through an impact motor having a modified cross section of the anvil.FIG. 12, finally, shows a cross section through a further modificationof the impact motor.

The impact tool in FIG. 1 comprises a back piece 10 provided with ahandle 11 and a front piece 12. The front piece 12 encloses the rotaryimpact motor and is provided with a central forward journalling bore 13through which an anvil 14 projects rotatably.

In the back piece 10 is affixed a rotary suitably powered conventionaldrive motor, preferably a reversible pneumatic vane motor comprising arotor 15 carrying radial vanes, not shown. The rotor 15 is rotated inusual manner by compressed air delivered to the vanes of the motor, theair being suitably supplied through the handle 11. The rotor iscontrolled by a throttle valve, not shown, and a conventional reversingslide 16.

The forward end of the rotor is journalled in a ball bearing 17 andcarries straight axially extending splines 18. The forward end of theanvil. 14 has a polygonal end portion 20 for carrying a suitable toolsuch as a socket Wrench, not shown. In the journalling bore 13 the anvil14 is journalled by a cylindrical portion 21 which within the frontpiece 12 passes over into a radial cam 22. The rear end of the anvil 14has a cylindrical reduced portion 23, which carries rotatably acentering ring 24 which in its turn is rotatably supported by arotatable cylindrical drive means or element 25. The drive element 25has a recess 26 at the periphery thereof and a rearwardly directed hubportion 27 which by inner axial splines and grooves 19 is in engagementwith the splines 18 of the rotor 15, FIG. 3, and is carried by the rotor15.

A hammer body 30 is coaxially rotatably journalled about the anvil 14and fits by a forward journalling sleeve 3-1 rotatably on thecylindrical portion 21 of the anvil 14 behind the joumalling bore 13.The hammer body 13 is provided with a rotation cavity 32 coaxial withthe axis of rotation thereof which cavity surrounds the radial cam. 22of the anvil 14 and allows free rotation of the latter in the rotationcavity 32. Out into the rotation cavity 32- there opens a journallingrecess 33 provided by a cylinder surface which has a larger diameterthan the rotation cavity 32 and receives an impact dog 34 arcuatelyarched in cross section. The impact dog has a partly cylindrical convexback portion 35 extending over more than 180 degrees. The impact dog 34is at the back portion thereof slidably supported along the entirelength thereof by the cylinder surface of the journalling recess 33 forpivoting about an axis coaxial with said cylinder surface and fallingwithin the rotation cavity 32 and further extending in parallel butspaced relation to the axis of rotation of the hammer body 30. Therotation cavity 32 is terminated rearwardly by an enlarged cylindricalportion 36 which rotatably takes support against the periphery of thedrive element 25.

The radial cam 22 of the anvil 14 has in the embodiment according toFIGS. 1-7 a single lobe which is bordered symmetrically by two camflanks 37, 38 facing the two opposite rotational directions of the anvil14, which flanks provide the impact surfaces of the anvil 14 and passover into a cylindrical cam ridge 39 coaxial with the axis of rotationof the anvil 14. The impact dog 34 is recessed by a concave recess 40facing the anvil 14 which recess may have an arbitrary suitable shapebut preferably is formed by a cylinder surface concentric with the backportion 35 of the impact dog 34. The opposite outer portions of thecylinder surface of the recess 40' provide the impact surfaces of theimpact dog cooperating with the cam flanks 37, 38 of the anvil. The camflanks 37, 38 thus adapted for cooperation with the cylindrical recess40 are shaped partly cylindrical having the same radius of curvature asthe recess 40- and extend with the provision of necessary operatingclearance along cylindrical surface which has the same diameter as therecess 40 of the impact dog 34. The cam flanks 37, 38 pass over with asuitable fillet radius into the cylindrical base portion 53 of theradial cam 22.

The recess 40 of the impact dog 34 is separated from the back portion 35by straight end surfaces 41, 42 transverse to the back portion and tothe recess 40 intersecting the latter under a blunt angle along axialcam edges 43, 44 which in case of need may be slightly rounded. The camedges 43, 44 and the end surfaces 41, 42 provide cam following means forthe impact dog cooperating with the radial cam 22 in a manner describedhereinafter.

The forward end of the impact dog 34 is supported head-on against aplane bottom surface 54, FIGS. 1, 2, in the journalling recess 33. Therear end of the impact dog 34 has a central extension 45 which mateswith the recess 26 of the drive element 25 and is in camming engagementwith the latter.

Let it be supposed that the rotor 15 in operation rotates the rotaryimpact motor and the anvil 14 thereof clockwise via the drive connectionconsisting of the splines and grooves 18 and 19 and that the polygonalend portion 20 of the anvil 14 via a socket wrench, not shown, transmitsthe rotation to a threaded fastener. If the parts of the rotary impactmotor are in the position depicted in FIGS. 3 and 4, the recess 40 ofthe impact dog 34, as long as the screw rotates easily, will remain inimpact position in engagement with the flank 37 of the radial cam 22,and the rotation of the drive element 25 is thus transmitted at itsrecess 26 and the extension 45 of the impact dog 34 to the impact dog 34and thence via the radial cam 22 to the anvil 14, the socket wrench, andthe fastener. Thus the impact dog 34 transmits the rotation to theradial cam 27 via the portion thereof trailing in the rotationaldirection in which direction the corresponding cylinder surface portionof the recess 40 provides the driving Surface. It is true that the driveelement 25 during driving strives to pivot the impact dog 34 over thecam ridge 39 to release position, FIGS. 5, 6, by the driving engagementbetween the recess 26 and the extension 45, FIG. 3, striving inlever-manner to turn the impact dog 34 around the cam flanks 37, 38,which in the position depicted in FIG. 4 are substantially centered onthe geometrical axis of the journalling recess 33. Due to frictionbetween the impact dog 34 and the radial cam 22 these parts, however,remain in engagement with one another substantially in the positionshown in FIGS. 3, 4, so that the fastener is rotated continuously untilit has been screwed down and the resistance to rotation increasessharply.

At sufliciently large rotational resistance the anvil 14 stops, therotor 15, however, forcing the drive element to continue its rotation.This causes the impact dog 40 through cam action between the recess 26and the extension 45 of the impact dog 34 to pivot over the radial cam22 from the impact position in FIGS. 3, 4 to release position in FIGS.5, 6. The end surface 41 of the impact dog 34 leading in the rotationaldirection is turned to abut against the base portion 53 of the radialcam 22 beyond the flank 38 and the leading end surface 41 and its camedge 43 are successively forced to slide around the base portion 53while the hammer body 13 is rotated by the drive element 25 about theanvil 1-4 in an accelerated movement. The acceleration course isillustrated in FIGS. 7-9. Near the end of the acceleration cycle the endsurface 41 of the impact dog 34 leading in the rotational direction runsup onto the flank 37, FIG. 8, of the radial cam 22 which causes areverse turning of the impact dog 34 about its pivotal axis, followed bya simultaneously performed forward turning and further acceleration ofthe hammer body 30 in the rotational direction beyond the accelerationdelivered thereto by the drive element 25. When the end surface 41 haspassed the flank 37 its cam edge 43 runs up onto the cam ridge 39, FIG.9, of the radial cam which is concentric with the anvil 14 and with theaxis of rotation of the hammer body 30. As a result the impact dog 34 isretained positively in impact position by the cam edge 43 taking supportagainst the cam ridge 39 until delivery of an impact. Immediatelythereupon the lmpact dog 34, FIGS. 3, 4, delivers its impact against thecam flank 37 by the portion of the recess 40 thereof trailing in therotational direction so that the kinetic energy of the hammer body 30 isdelivered against the anvil 1.4 in the form of a rotational impacttransmitted to the socket wrench and the fastener. In direct sequence tothe impact the impart dog 34 normally rebounds slightly to the reversewith respect to the cam. flange 37 while the cam edge 43 continues tokeep the impact dog 34 positively in the impact position. At the nextweak impact against the cam flank 37 the impact dog 34- is free to pivotas a result of the engagement between the recess 26 of the drive element25 and the extension 45 of the impact dog 34 over the ridge 39 of theradial cam 22 to the position shown in FIGS. 5, 6. Thereupon the nextacceleration and impact cycles are performed in analogy with the abovedescribed until the desired tightening torque has been reached in thefastener.

The symmetrical design of the rotary impact motor allows analogousimpact action at counter-clockwise rotation as well. At such instant theimpacts are delivered against the cam flank 38 by the portion of therecess 40 of the impact dog 34 trailing in the rotational direction,while the end surface 42 of the impact dog 34 leading in the rotationaldirection causes turning of the impact dog to impact position and itscam edge 44 by positive cooperation with the cam ridge 39 maintains theimpact dog in impact position before and until the delivery of animpact.

In the embodiment of FIGS. 10, 11 the radial cam 22 of the anvil 14 isdesignated with two lobes 46, 47 each carrying one of the cam flanks 37,38. The other parts of the rotary impact motor are analogous with theparts of the embodiment in FIGS. 19. To the lobes 46, 47 are connectedcam ridges 48, 49 concentric with the axis of rotation of the anvil 14which ridges, however, are shortened and pass over into the back-portion50 of the radial cam, said back portion being angularly bluntlyflattened. The back portion 50 and the shortened cam ridges 48, 49 areshaped such that the back portion 50 of the radial cam can be passed bythe impact dog 34 during rotation of the hammer body 30 around the anvil14. As apparent from FIG. the impact dog 43, by reason of the cam ridge48 being shortened, will be positively guided at the cam edge 43 duringa shortened portion of the movement of the impact dog 37 up to impactposition which, however, is sufficient for assuring that a sufficientlylarge portion of the recess 40 hits the respective cam flanks 37, 38.The modified embodiment has a more advantageous shape when it comes tostrength considerations of the radial cam 22 and of anvil 14. During thepassage of the impact dog 34 past the back portion 50 and over the nextlobe 47 (or 46 during rotation in opposite direction), the impact dogperforms a swinging movement without impact action which causes acertain loss of energy.

In the embodiment of FIG. 12 the radial cam 22 has straight plane camflanks 37, 38. The concave recess 40 of the impact dog 34 consists of apair of plane impact surfaces 51, 52 which form a nearly straight,slightly acute angle with the end surfaces 41, 42 and over a suitablefillet radius are connected to a central plane 55 perpendicular to thecentral plane of symmetry of the impact dog. In its operation the impactmotor of FIG. 12 is analogous with the other above describedembodiments.

A central plane similar to the plane 55, FIG. 12, preferably withoutfillet radii, may in case of need be arranged on the impact dog 34depicted in FIGS. l9 allowing to provide an increased thickness at thearcuate portion of the impact dog 34.

I claim:

1. A rotary impact motor with impact action in both rotationaldirections thereof comprising a housing, a rotatable anvil in saidhousing, opposed impact surfaces on said anvil, a hammer body rotatablycarried in said housing coaxially with respect to the axis of rotationof said anvil, a rotation cavity in said hammer body surrounding saidanvil and said impact surfaces thereof, a partly cylindrical journallingrecess in said hammer body opening up into said rotation cavity thereofand of larger diameter than said rotation cavity, an impact dog having arecess thereon facing said anvil and a partly cylindrical back portionextending over more than degrees and supported in said journaling recessfor pivotal movement about an axis spaced from but parallel with saidaxis of rotation for taking respectively impact or release positionrelative to one of said impact surfaces, opposed end surfaces on saidimpact dog transverse to said back portion and said recess thereof, oneof said surfaces cooperating with said anvil for pivoting said impactdog to said impact position, and rotatable drive means in said housingin operative engagement with said impact dog for pivoting said impactdog to said release position.

2. A rotary impact motor according to claim 1 in which said impactsurfaces are a pair of radial cam flanks facing opposite directions ofrotation, the end surface of said impact dog leading in the rotationaldirection during ro tation of said hammer body relative to said anvilcooperating with the cam flank meeting the rotation thereof for pivotinga portion of the surface forming the recess of said impact dog to impactposition aganst that same cam flank.

3. A rotary impact motor according to claim 2 in which the impactingportions of the surface forming said recess of the impact dog are formedby a cylinder surface concentric with said back portion of said impactdog.

4. A rotary impact motor according to claim 2 in which said radial camflanks form part of a radial cam having a ridge connected to therespective cam flank and coaxial with the axis of rotation of saidanvil, cam edges on the impact dog at the intersection between saidrecess and said end surfaces thereof, and the cam edge leading in therotational direction cooperating with said cam ridge for positivelretaining said impact dog in the impact position prior to the deliver ofan impact.

5. A rotary impact clutch according to claim 3 in which said cam flanksare partly cylindrical having substantially the same radius of curvatureas said cylinder surface forming said recess of said impact dog.

6. A rotary impact motor according to claim 5 in which said cam flanksform part of a single cam lobe extending with the provision of operatingclearance along a cylindrical surface of equal diameter with thecylinder surface forming the recess of said impact dog.

7. A rotary impact motor according to claim 4 in which said cam edgesare blunt.

References Cited UNITED STATES PATENTS 2,343,596 3/1944 Van Sittert etal. l7393.5 2,768,546 10/1956 Amtsberg 173-93.5 3,129,796 4/1964 Karden173--93.5 3,533,479 10/1970 Madsen et a]. 17393.5

JAMES A. LEPPINK, Primary Examiner

